HTTP mIRC IRC URL BO

Severity: High

This attack could pose a serious security threat. You should take immediate action to stop any damage or prevent further damage from happening.

Description

This signature detects an attempt to exploit a buffer overflow vulnerability in mIRC which may result in remote code execution.

Additional Information

mIRC is a chat client for the IRC protocol, designed for Microsoft Windows based operating systems. When mIRC is installed it registers a handler for a 'irc://' type of URL. Through these means, mIRC is invoked when a 'IRC URL' is followed.

mIRC has been reported prone to a buffer overflow vulnerability when handling malicious 'IRC URLs'. Specifically when a IRC URL of >998 bytes is clicked by a user running a vulnerable version of mIRC.

The issue likely presents itself due to a lack of sufficient boundary checks performed when IRC URL data is being copied into an insufficient buffer in memory. Data that exceeds the size of the reserved buffer will overrun its bounds and corrupt adjacent memory. Because memory adjacent to the affected buffer is used to store a saved instruction pointer, an attacker may influence execution flow of the affected client into attacker controlled memory. This may ultimately allow the attacker to execute arbitrary instructions in the context of the user running the affected client.

mIRC version 6.1 has been reported to be prone to this issue, however other versions may be affected as well.